Engine-driven electric generating plant



Patented Jan. 22, 1952 EN GINE-DRIVEN ELECTRIC GENERATING PLANT Johann Hermann Abbink-Spaink, Bradford, England, assignor to The English Electric Company Limited, London, England, a British com- Application September 20, 1949, Serial No. 116,785 In Great Britain February 16, 1949 15 Claims. 1 I My invention relates, generally, to enginedriven electric generating plants and, more particularly, to plants of this kind which are utilized to supply power to the traction motors of locomotives.

An object of my invention, generally stated, is to provide a control system for diesel-electric locomotives which shall be simple and efiiclei in operation and which may be economically manufactured and installed.

A more specific object of my invention is to provide for weakening the excitation of the traction motors of a diesel-electric locomotive under predetermined conditions, whereby higher running speeds may be obtained.

A further object of my invention is to provide for automatically initiating field weakening of the traction motors when the engine fuel regulator is at its maximum setting and the generator at maximum excitation.

Another object of my invention is. to provide for weakening the excitation of the traction motors in successive steps.

A still furtherobject of my invention is to provide for adjusting the engine load when field weakening is initiated.

Other objects of my invention will be explained. fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of my invention, the field weakening or shunting of the traction motors supplied by the engine-driven generator of a locomotive is initiated by control means responsive to the condition at which the engine fuel regulator is at its maximum setting. and the generator is at maximum excitation. Two successive stages of field weakening are provided and the engine load is adjusted when field weakening is initiated.

For a better understanding of the nature and objects of my invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which the single figure is a diagrammatic view of a control system embodying the principal features of the invention.

Referring to the drawing, a main generator H], which is driven by an engine E, is connected to supply current to a traction motor ll having a series field winding Ila across which two field weakening resistors l2 and I3 may be connected by means of contact members DCla and DCZa of contactcrs DC! and DCZ, respectively, A field winding lea of the generator (0 is connected through a rheostat I4, which is operated by a rei versible motor l5, and a series resistance It across a direct-current source of supply. The resistance It is normally short-circuited by contact members PS6 of a contactor F8.

The reversible motor 15 is controlled by an engine governor 18 which controls a throttle mechanism l1 and is also utilized to provide torque control. The governor i8 is disposed to operate, either directly or through a servo-mechanism, a switch 19 which controls the energization of relays VR and VL. Contact members VR! and VLI of the relays VR and VL, respectively, are con-. nected in series-circuit relation with two op posed field windings l5a and I5b, respectively, on the motor l5. If the engine speed decreases, the rheostat I4 is automatically actuated in a direction to reduce the excitation of the generator. Conversely, if the engine speed rises, the rheostat I4 is automatically actuated in a direction to increase the excitation of the generator.

Field weakening of the traction motor II is automatically effected in two successive stages when a drivers controller 20 is in the position for supplying maximum fuel to the engine and the field rheostat I4 is actuated to the position corresponding to maximum excitation of the generator. A predetermined maximum current in the traction motor causes a current relay OR to operate whereby the motor field is returned to full excitation by successive stages.

When the drivers controller 20 is in the maximum position, a circuit is completed from posite through a segment 280. on the controller and normally closed contact members DC2b of the contactor D02 to a relay TR. This relay accordingly operates to open its contact members TRI and close its contact members TR2, thereby bringing the field contactor FS under the control of a limit switch LS having contact members LR disposed to open when the field rheostat M attains the position corresponding to maximum generator excitation. The contact members TRI and TRZ of the relay TR are disposed to so overlap that the operation of the relay TR does not open the contactor FS, the energizing circuit for its coil being maintained through the contact members TRZ and F81.

Deenergization of the contactor FS by the opening of the limit switch LR results in the energization through interlock contact members FSI of a delayed opening relay H which operates to close its three sets of contact members HI H2 and H3. Deenergization of the contactor FS also results in the opening of the contact members F85 whereby resistor I6 is connected into the cira cuit of the generator field winding ifla. When this resistance is inserted in the circuit the generator field collapses rapidly. Also the relay VL is energized by contact members FS5 closing so that the rhecstat I4 is actuated backwardly, thereby immediately reclosing the limit switch LR. The backward movement of the rhecstat I4 is limited by the limit switch LL. When the generator voltage has dropped to a predetermined value, a relay DR which is connected across the generator armature drops out. The resulting closure of contact members DR! of the relay DR. completes a circuit through contact members TRZ and limit switch LR to reenergize the field contactor FS.

The insertion of resistance iii in the main generator field circuit and the increase of resistance of the rhecstat M reduce the load on the diesel engine with a consequent increase of speed. The servo-mechanism of the engine governor would. therefore, remain in the voltage raise position. Accordingly, during transition into the intermediate and weak fields, while the field contactor is deenergized, this servo-mechanism is isolated by contact members PS4 which are open during the transition period.

Reenergization of the contactor FS results in again short-circuiting the field-resistor I6 at the contact members FSB. It also results in a circ it being com leted through contact members F82 and Hi to the contactor DCI which closes its contact members DCla to connect the resistance [2 in parallel-circuit relation with the traction motor field winding I a. thereby completing the first stage of field weakening.

It will be noted that while the energization of the contactor FS results in the deenergization of the relay H by the opening of contact members FSi, the opening of contact members HI will be delayed by the short-circuited winding on the relay H. By the time the contact members HI o en contactor DCI will have closed and completed a maintaining circuit for itself through contact members DCib, the relay contact members CR! and a segment Ziib on the controller 26. It will also be noted that there is no circuit completed to the contactor D02 since the contact members RI of a delayed opening relay R do not close until the relay is deenergized. This relay is not deenergized until the relay H has opened its contact members H3.

The next stage of field weakening is obtained when, with the drivers controller in the maximum position, the rhecstat [6.- again reaches the position corresponding to maximum generator excitation. When this occurs the limit switch LR is again opened and, contact members TRZ being closed, the contactor FS is again deenergized and the resistance l6 again inserted in the circuit for the field winding Hla of the generator. The generator voltage accordingly drops rapidly until the relay DR operates to reestablish a circuit through its contact members DRI, the limit switch LR (now closed) and contact members TR2 to the field contactor FS.

Energization of the contactor FS now results in the completion of a circuit through contact members F83, H2 and Rl to the fieldcontactor DC2 which operates to close its contacts DCZa, h y connecting the resistance [3 in parallelcircuit relation with the motor field winding Ila to complete the second stage of field weakening, Closure of the contactor DCE also results in th pletion of a maintaining circuit for itself,

through contacts D020, CR2 and segment 200 on the drivers controller 20.

It will be noted that since the contactors DCI and D02 have their maintaining circuits completed through sectors on the drivers controller any stage of field weakening, once it has occurred, can be maintained although the driver moves the control handle back from the maximum position.

Assuming that two stages of field weakening have been initiated and that contactors DCI and D02 are energized, a certain predetermined load on the traction motor I I will cause the relay CR to open its two normally closed contact members CRI and CR2. The opening of contact members CR2 interrupts the maintaining circuit for the contactor DC2 which accordingly opens to remove the resistor l3 from the motor field circuit, thereby returning the equipment to the first stage of field weakening.

However, the maintaining circuit for contactor DCI is not interrupted by the opening of contact members CRI because these contact members are bridged by contact members R2 of the delayed opening relay R. This relay, which was energized through contact members DC2d while contactor D02 was closed, maintains its contact members closed for a few seconds after its coil is deenergized. By the time the contact members R2 open the traction motor current will have dropped to a value at which the contact members CRI and CR2 of the current relay CR are again closed. Unless the traction motor current again exceeds the predetermined value the equipment remains with one stage of field weakening in action.

The next time the contact members CRI and CR2 open on account of heavy currents in the traction'motor the contactor DC! is immediately opened because the normally open contact member R2 in its maintaining circuit is now open.

The opening of this contactor returns the equipment to full motor excitation.

It will be noted that the function of changing back from weak field to full field obtains equally with the drivers controller 20 in the maximum position as well as with the handle moved backward slightly.

When changing from full field into weak field the contactor FS is opened, thereby inserting the resistor [6 into the generator field circuit and causing a rapid decrease in the excitation of the generator field. At the same time the opening of the contactor FS causes the field rheostat [4 to move in the direction providing less excitation for the generator field. Changing to the weak field of the traction motor occurs as soon as the generator voltage has dropped to a predetermined amount, and a control rhecstat 2| has been provided in the circuit for the coil of the relay DR in order that the voltage at which the relay DR drops out can be preset.

As long as the contactor FS is energized, the rhecstat 2| is short-circuited by contact members FS8 but as soon as the contactor FS opens the rhecstat 2| it connected into the circuit for the coil of the relay DR. The resistance of this rhecstat can be set to cause the relay DR to open immediately when the contactor FS opens, in which case the engine load would be at a maximum. On the other hand, the engine load control rhecstat can be so set that when the con tactor FS opens, the field rheostat [4 will have to lower excitation of the generator to such an extent before the relay DR drops out that there will be no engine load whatsoever at the moment of changing to the weak field connections. Therefore, the engine load control rheostat provides a means for readily adjusting the allowable engine load during the period of transition to the weak field connections for the traction motors.

As already mentioned, the field weakening cannot be initiated unless the drivers controller is in the maximum position. However, once one or two stages of the field weakening has occurred the moving back of the drivers control handle maintains such stages of field weakening as have been obtained while the control handle was in the maximum position.

It will be noted that each stage has its own maintaining sectors associated with the drivers controller and by making these sectors of unequal length the control can be inherently so made that two stages of field weakening are dropped successively, as the control handle is moved away further and further from the maximum position. However, both stages oi field weakening are at all times subject to the automatic control of the current relay CR, as previously explained.

It wili be noted that when the drivers controller handle is in the maximum position, the first stage of the field weakening is obtained by the closing of the contactor DCl, as previously explained, and that after the closure of this contactor the drivers handle can be moved slightly backward, thereby preventing the obtaining of the second stage of field weakening. If the driv ers control handle is moved again to the maximum position the equipment is capable of obtaming the second stage of field weakening under correct conditions.

It will also be noted that when the drivers control handle is held in the maximum position. one or both stages of field weakening can automatically come in and go out and come in again according to the operating conditions prevailing. Thus, the field weakening is automatically controlled in accordance with the operatingconditions.

From the foregoing description, it is apparent that I have provided a system for automatically obtaining field weakening of the traction motors of a diesel-electric locomotive, or similar vehicle, in a plurality of stages. The field weakening is initiated when the generator which supplies the traction motors is at its maximum excitation and the engine fuel regulator is at its maximum setting.

Since numerous changes may be made in the above described construction and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I- claim as my invention:

1. In a control system, in combination, a motor having a field winding, a generator for supplying current to the motor, an engine for driving the generator, shunting means for the motor field winding, control means for controlling the generator excitation, switching means controlled by said control means for controlling the operation of said field shunting means, and relay means repsonsive to the motor current for also controlling the operation of said field shunting means.

2. In a control system, in combination, a motor having a field winding, 2. generator for supplyin; current to the motor. an engine for driving the generator, an engine fuel controller, shunting means for the motor field winding, control means for controlling the generator excitation, switching means for controllingthe operation of said field shunting means, said fuel controller and said control means cooperating to control the operation of said switching means, and relay means responsive to the motor current for also controlling the operation of said field shunting means.

3. A power-plant comprising an electric motor having a series main-field winding, a variable- "voltage generator supplying substantially all of its output-current to the motor, said generator having controllable main-field winding, a controila engine supplying substantially all of its output-power for driving the generator, an engine-controller under the control of an engineman, a variable-adjustment controlling-means for controlling the excitation of the generator main-field winding, shunting-means including at least one field-shunt adapted for connection in parallel-circuit relation across the series mainfield winding of the motor, and field-shunting relaymeans, responsive to a maximum-excitation position of said generator-field controlling-means, and responsive also to a maximum-power setting the enginecontroller,'for connecting an effective field-shunt across said series main-field windof the motor.

4. A power-plant comprising an electric motorhaving a series main-field winding, a variablevoltage generator supplying substantially all of its output-current to the motor, said generator having a controllable main-field winding, a controllable engine supplying substantially all of its output-power for driving the generator, an engine-controller under the control of an engineman, a variable-adjustment controllingnneans for controlling the excitation of the generator main-field winding, shunting-means including at least one field-shunt adapted for connection in parallel-circuit relation across the series mainfield winding of the motor, and field-shunting relay-means, responsive to a maximum-excitation position of said generator-field controllingmeans, and responsive also to a maximum-power setting of the engine-controller, for connecting an effective field-shunt across said series mainfield winding of the motor and reducing the gencrater-excitation.

5. The invention as defined in claim 4, in com bination with means, responsive to a predetermined operating-condition, for cutting out an effective field-shunt from its shunting connection across said series main-field winding of the motor in time to prevent sustained overloading during a shunted-field operating-condition of the motor.

6. A power-plant comprising an electric motor having a series main-field winding, a variablevoltage generator supplying substantially all of its output-current to the motor, said generator having a controllable main-field Winding, a con trollable engine supplying substantially all oi its output-power for driving the generator, an engine-controller under the control of an engineman, an excitation-means responsive to the engine-speed, for controlling the excitation of the generator main-field winding, shunting-means including at least one field-shunt adapted for connection in parallel-circuit relation across the series main-field winding of the motor, and fieldshunting relay-means, responsive to an operatingcondition accompanied by a substantially maxi- 7 mum generator-voltage, for first reducing the generator-excitation and immediately afterwards connecting an effective field-shunt across said series main-field winding of the motor.

7. The invention as defined in claim 6, in combination with means, responsive to a predeter-- mined operating-condition, for cutting out an effective field-shunt from its shunting connection across said series main-field winding of the motor in time to prevent sustained overloading during a shunted-field operating-condition of the motor.

8. A power-plant comprising an electric motor having a series main-field winding, a variablevoltage generator supplying substantially all of its output-current to the motor, said generator having a controllable main-field winding, a controllable engine supplying substantially all of its output-power for driving the generator, an engine-controller under the control of an engineman, a controlling-means for controlling the excitation of the generator main-field winding, shunting-means including at least one field-shunt adapted for connection in parallel-circuit relation across the series main-field winding of the motor, and field-shunting relay-means, responsive to an operating-condition accompanied by a substantially maximum generator-excitation and a maximum-power setting of the engine-com troller, for first reducing the generator-excitation and immediately afterwards connecting an effective field-shunt across said series main-field winding of the motor.

9. The invention as defined in claim 8, in combination with means, responsive to a predetermined operating-condition, for cutting out an effective field-shunt from its shunting connection across said series main-field winding of the motor in time to prevent sustained overloading during a shunted-field operating-condition of the motor.

10. A power-plant comprising an electric motor having a series main-field winding, a variable-voltage generator supplying substantially all of its output-current to the motor, said generator having a controllable main-field winding, a controllable engine supplying substantially all of its output-power for driving the generator, an engine-controller under the control of an engineman. an excitation-means, responsive to the engine-speed, for controlling the excitation of the generator main-field winding, a multi-step adjustable field-shunting means, adapted for connection in parallel-circuit relation across the series main-field winding of the motor, fieldshunt increasing-means, responsive to successive attainments of one predetermined operatingcondition accompanied by a maximum excitation-condition of the generator-field excitationmeans and a maximum-power setting of said engine-controller, for connecting said fieldshunting means in successive steps, at least one such step in response to each such attainment, across said series main-field winding of the motor, and field-shunt decreasing-means, re sponsive to successive attainments of another predetermined operating-condition, for disconnecting said field-shunting means in successive steps, at least one such step in response to each such attainment, from its shunting connection across said series main-field winding of the motor, in time to prevent sustained overloading during a shunted-field operating-condition of the motor.

11. The invention as defined in claim 10, characterized by said field-shunt increasing means including voltage-responsive resettingmeans, responsive to a predetermined drop in the voltage of the generator after a shunt-increasing operation, for resetting said field-shunt increasing-means in readiness for another shunt-increasing operation.

12. A power-plant comprising an electric motor having a series main-field winding, a variable-voltage generator supplying substantially all of its output-current to the motor, said generator having a controllable main-field winding, a controllable engine supplying substantially all of its output-power for driving the generator, an engine-controller under the control of an engineman, a variable-adjustment controllingmeans for controlling the excitation of the generator main-field winding, a multi-step adjustable field-shunting means, adapted for connection in parallelcircuit relation across the series main-field winding of the motor, field-shunt in" creasing-means, responsive to successive attainments of a maximum excitation position of said generator-field controlling-means, and respon-' sive also to a maximum-power setting of the engine-controller, for connecting said field-shunting means in successive steps, at least one such step in response to each such attainment, across said series main-field winding of the motor, and field-shunt decreasing-means, responsive to successive attainments of another predetermined operating-condition, for disconnecting said field shunting means in successive steps, at least one such step in response to each such attainment, from its shunting connection across said series main-field winding of the motor, in time to prevent sustained overloading during a shuntedfield operating-condition of the motor.

13. A power-plant comprising an electric motor having a series main-field winding, a variable-voltage generator supplying substantially all of its output-current to the motor, said generator having a controllable main-field winding, a controllable engine supplying substantially all of its output-power for driving the generator, an engine-controller under the control of an engineman, an excitation-means, responsive to the engine-speed, for controlling the excitation of the generator main-field winding, a multi-step adjustable field-shunting means, adapted for connection in parallel-circuit relation acrcss the se ries main-field winding of the motor, field-shunt increasing-means, responsive to successive attainments of one predetermined operating-com dition accompanied by a maximum excitationcondition of the excitation-means and a maximum-power setting of said engine-controller, for connecting said field-shunting means in successive steps, at least one such step in response to each such attainment, across said series mainfield winding of the motor, each time also causing a reduction in the excitation produced by the excitation-means, and field-shunt decreasingmeans, responsive to successive attainments of another predetermined operating-condition, for disconnecting said field-shunting means in successive steps, at least one such step in response to each such attainment, from its shunting con nection across said series main-field winding of the motor, in time to prevent sustained overloading during a shunted-field operating-condi tion of the motor.

14. The invention as defined in claim 13, char acterized by said field-shunt increasing-means including voltage-responsive resetting-means. responsive to a predetermined drop in the voltage of the generator after ashunt-increasing opera-- tion, 'torlresetting said field-shunt increasingmeans in readiness for another shunt-increasing operation. a

15. A power-plant comprising an electric motor having a series main-field winding, a variable-voltage generator supplying substantially all of itsfoutput-current to the motor, said generatorghalving a controllable main-field winding, a, controllable engine supplying substantially all of its output-power for driving the generator, an engine-controller under the control of an engineman", a variable-adjustment controllingmeans for controlling the excitation of the generatormain-field winding, a multi-step adjustable field-shunting means, adapted for connection in parallel-circuit relation across the series main-field winding of the motor, field-shunt increasing-means, responsive to successive attainments of amaximum-excitation position of said generator-field controlling-means, and responsive also to a maximum-power setting of the engine-controller, for connecting said fleld-shunting means in successive steps, at least one such step in response to each such attainment, across said series main-field winding of the motor, each time also causing a reduction in the setting of the generator-field controlling-means, and field shunt decreasing-means, responsive to successive REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,657,239 Clymer Jan. 24, 1928 1,833,017 Cutler NOV. 24', 1931 2,245,083 Webb 81; al June 10, 1941 2,290,367 Curry July 28, 1942 2,292,203 Cowin Aug. 4, 1942 2,433,628

Schlapfer Dec. 30, 1947 

